dttlCKEN CilOLERA. 71 



"Let us take a fowl -which is about to die of chicken cholera, and let us dip 

 the end of a glass rod in the blood of the fowl with the usual precautions, upon 

 which I need not here dwell. Let us then touch, with this charged point; some 

 chicken broth, very clear, but rendered sterile under a temperature of 115° 

 Centigrade, and under conditions in which neither the outer air nor the vessels 

 employed can introduce exterior germs — these germs which are in the air or on 

 the surface of all objects. In a short time if the little culture-vase is placed in 

 n temperature of 25° to 35°, you will see the liquid become turbid, and full of 

 tiny microbes, shaped like the figure 8, but often so small that, under a high 

 magnifying powei- they appear like points. ^ Take from this vase a drop as small 

 »s you please — no more than can be carried on the point of a glass rod as sharp 

 OS a needle — and touch with that point a fresh quantity of sterilized chicken 

 broth placed in a second vase, and the same phenomenon iB produced. You deal 

 in the same way with a third culture-vase, with a fourth, and so on to a hundred, 

 or even a thousand, and invariably, within a few hours, the olilture liquid 

 becomes turbid andi filled with the same minute organisms. At the end of two 

 or three days' exposure to a temperature of about 30° Centrigrade, the thickness 

 of the liquid disappears, and a sediment is formed at tjie bottom of the vase. 

 This signifies that the development of the minute organism has ceased; in other 

 words, all the little points which caused the turbid appearance of the liquid 

 have fallen to the bottom of the vase, and things will remadu in this condition for 

 a longer or shorter time — for months even — without either the liquid or the de- 

 posit undergoing any visible modification, inasmuch as we have taken care to ex- 

 clude the germs of the atmosphere. A little stopper of cotton sifts the air which 

 enters or issues from the vase through changes of temperature. 



" Let us take one of our series of culture preparations^r-the hundredth or the 

 thousandth, for instance— and compare it, in respect to its virulence, with the 

 blood of a fowl which has died of cholera; in other words, let,us inoculate undei 

 the skin ten fowls, for instance, each separately with a drop of infectious blood, 

 and ten others with a similar quantity of the liquid in which the deposit has first 

 been shaken up.. Strange to say, the latter ten fowls wiU die as quickly,^ and 

 with the same symptoms as the former ten ; the blood of all will be found to 

 contaiii after death the same minute infectious organisms. 



"Let us how repeat exactly our successive cultures, with this single difference, 

 that we pass from one culture to that which follows it — say from the one hun- 

 dredth to -the one hundred and first, at intervals of a fortnight, or one, two or 

 three months. If, now, we compare the virulence of the successive cultures, a 

 great change will be observed. It will be readily seen, from an inoculation of a 

 series of ten fowls, that the virulence of one culture differs from that of the 

 blood, and from that of a preceding culture, when a sufficiently long interval 

 elapses between the impregnation of one culture with the microbe of the pre- 

 M^ding. More thap this, we may recognize by this mode of observation j that it 

 is possible to prepare cultures of varying degrees of virulence. -One preparation 

 will kill eight fowls out of ten ; another, five out of ten ; another, one out of ten ; 

 another, none at all, although the microbe may still be cultivated. In fact, what 

 is no less strange, if you take each of these cultures of attenuated virulence as 

 a point of departure in the prepara/tion of successive cultures, and without ap- 



